[libhid-discuss] reading from a barcode scanner that acts like a keyboard

[Brice Rebsamen]

Hello,

I have a USB barcode scanner that acts like a keyboard: whenever a barcode
is read it sends the code where the keyboard would normally write. I am
writing some code in C to read from the scanner.

I initialliy tried with libusb (and failed) but since the scanner acts like
a keyboard I figured I would be more successful with libhid. Can someone
tell me how to read from that scanner/keyboard using libhid?

Below is the output of usbview, test_libhid and lsusb

Thanks,
Brice


$ usbview
Symbol Bar Code Scanner
...
Speed: 12Mb/s (full)
USB Version: 1.10
Device Class: 00(>ifc )
Device Subclass: 00
Device Protocol: 00
Maximum Default Endpoint Size: 8
Number of Configurations: 1
...
Config Number: 1
   Number of Interfaces: 1
   Attributes: 80
   Max Power Needed: 400mA

   Interface Number: 0
      Name: (none)
      Alternate Number: 0
      Class: 03(HID )
      Sub Class: 1
      Protocol: 1
      Number of Endpoints: 1

         Endpoint Address: 81
         Direction: in
         Attribute: Int.
         Max Packet Size: 8
         Interval: 10ms


$ test_libhid
parse tree of HIDInterface 002/004[0]:
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000 ; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000 ; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x90
 path: 0x00010006.0x00000000; type: 0x90
 path: 0x00010006.0x00000000 ; type: 0x90
 path: 0x00010006.0x00000000; type: 0x90
 path: 0x00010006.0x00000000; type: 0x90
 path: 0x00010006.0x00000000; type: 0x90
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000 ; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80
 path: 0x00010006.0x00000000; type: 0x80



$ lsusb -s 2:4 -vvv
Bus 002 Device 004: ID 05e0:0200 Symbol Technologies
Device Descriptor:
 bLength                18
 bDescriptorType         1
 bcdUSB               1.10
 bDeviceClass            0 (Defined at Interface level)
 bDeviceSubClass         0
 bDeviceProtocol         0
 bMaxPacketSize0         8
 idVendor           0x05e0 Symbol Technologies
 idProduct          0x0200
 bcdDevice            2.04
 iManufacturer           1 (c) Symbol Technologies, Inc, 2000
 iProduct                2 Symbol Bar Code Scanner
 iSerial                 3 S/N:2925e1000000 Rev:NBRXUAAM3
 bNumConfigurations      1
 Configuration Descriptor:
   bLength                 9
   bDescriptorType         2
   wTotalLength           34
   bNumInterfaces          1
   bConfigurationValue     1
   iConfiguration          0
   bmAttributes         0x80
     (Bus Powered)
   MaxPower              400mA
   Interface Descriptor:
     bLength                 9
     bDescriptorType         4
     bInterfaceNumber        0
     bAlternateSetting       0
     bNumEndpoints           1
     bInterfaceClass         3 Human Interface Devices
     bInterfaceSubClass      1 Boot Interface Subclass
     bInterfaceProtocol      1 Keyboard
     iInterface              0
       HID Device Descriptor:
         bLength                 9
         bDescriptorType        33
         bcdHID               1.10
         bCountryCode           33 US
         bNumDescriptors         1
         bDescriptorType        34 Report
         wDescriptorLength      65
         Report Descriptor: (length is 65)
           Item(Global): Usage Page, data= [ 0x01 ] 1
                           Generic Desktop Controls
           Item(Local ): Usage, data= [ 0x06 ] 6
                           Keyboard
           Item(Main  ): Collection, data= [ 0x01 ] 1
                           Application
           Item(Global): Usage Page, data= [ 0x07 ] 7
                           Keyboard
           Item(Local ): Usage Minimum, data= [ 0xe0 ] 224
                           Control Left
           Item(Local ): Usage Maximum, data= [ 0xe7 ] 231
                           GUI Right
           Item(Global): Logical Minimum, data= [ 0x00 ] 0
           Item(Global): Logical Maximum, data= [ 0x01 ] 1
           Item(Global): Report Size, data= [ 0x01 ] 1
           Item(Global): Report Count, data= [ 0x08 ] 8
           Item(Main  ): Input, data= [ 0x02 ] 2
                           Data Variable Absolute No_Wrap Linear
                           Preferred_State No_Null_Position
Non_Volatile Bitfield
           Item(Global): Report Count, data= [ 0x01 ] 1
           Item(Global): Report Size, data= [ 0x08 ] 8
           Item(Main  ): Input, data= [ 0x01 ] 1
                           Constant Array Absolute No_Wrap Linear
                           Preferred_State No_Null_Position
Non_Volatile Bitfield
           Item(Global): Report Count, data= [ 0x05 ] 5
           Item(Global): Report Size, data= [ 0x01 ] 1
           Item(Global): Usage Page, data= [ 0x08 ] 8
                           LEDs
           Item(Local ): Usage Minimum, data= [ 0x01 ] 1
                           NumLock
           Item(Local ): Usage Maximum, data= [ 0x05 ] 5
                           Kana
           Item(Main  ): Output, data= [ 0x02 ] 2
                           Data Variable Absolute No_Wrap Linear
                           Preferred_State No_Null_Position
Non_Volatile Bitfield
           Item(Global): Report Count, data= [ 0x01 ] 1
           Item(Global): Report Size, data= [ 0x03 ] 3
           Item(Main  ): Output, data= [ 0x01 ] 1
                           Constant Array Absolute No_Wrap Linear
                           Preferred_State No_Null_Position
Non_Volatile Bitfield
           Item(Global): Report Count, data= [ 0x06 ] 6
           Item(Global): Report Size, data= [ 0x08 ] 8
           Item(Global): Logical Minimum, data= [ 0x00 ] 0
           Item(Global): Logical Maximum, data= [ 0xff 0x00 ] 255
           Item(Global): Usage Page, data= [ 0x07 ] 7
                           Keyboard
           Item(Local ): Usage Minimum, data= [ 0x00 ] 0
                           No Event
           Item(Local ): Usage Maximum, data= [ 0xff 0x00 ] 255
                           (null)
           Item(Main  ): Input, data= [ 0x00 ] 0
                           Data Array Absolute No_Wrap Linear
                           Preferred_State No_Null_Position
Non_Volatile Bitfield
           Item(Main  ): End Collection, data=none
     Endpoint Descriptor:
       bLength                 7
       bDescriptorType         5
       bEndpointAddress     0x81  EP 1 IN
       bmAttributes            3
         Transfer Type            Interrupt
         Synch Type               None
         Usage Type               Data
       wMaxPacketSize     0x0008  1x 8 bytes
       bInterval              10
Device Status:     0x0000
 (Bus Powered)
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